Self-lowering jack



Ju 'zl 1925. 1,546,906

. J. c. 'KOPF SELF LOWERINQJACK Original Fileqi Feb. 4, 1921 4 Shets-Sheet 1 July 21 1925. I 1,546,906

. J. C. KOPF .SELF LOWERING JACK Original Filed Feb. 4, 1921 4 Sheets-Sheet 2 July 21 1925. 1,546,906

J. c. KOPF SELF LOWERING JACK O riginal Filed Feb. 4, 1921 4 Sheets-Sheet 5 33, flttome July 21 I925. 1,546,906

' J. C. KOPF SELF I-OWBRING JACK Original Filed Feb. 4, 1921 4 Sheets-Sheet 4 Patented July 21, 1925.

* UNITEDSTATES PATENT OFFICE.

JOI-IlWGi KOPF, OF AKRON, OHIO, ASSIGNOR TO THE DUFF MANUFACTURING COM- PANY, 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

snnr-nownnrue JACK.

Application filed February 4, 1921, Serial No. 442,365. Renewed January 16, 1925.

To all whom it may concern Be it known that 1, JOHN C. IQOPF, a citizen of the United States, and a resident of Akron, in the county of Summit and State of Ohio, have invented a new and use ful Self-Lowering Jack, of which the following is a specification. p 7

The object of the invention is to provide a simple, safe and reliable self-lowering screw-jack. Jacks are known wherein the load member is raised by a steep pitch screw and retarded in its descent by a dash-pot arranged in the ack casing and of which the load member forms one of the parts.

'" In such jacks the load is automatically held after each lifting stroke by a one-wayacting-clutch, and the load member can cou sequently be lifted beyond the liquid, in

which event there may be a substantially unchecked fall when'the holding device is released to permit lowering. According to this 1I1V611131'O11, a double-acting or contmuous-action daslrpot or fluid-retardingde,

viceis connected, through a onewayacting clutch, with the rotary run-down screw of the jack. In this way the cooperative relation between the holding device and the fluid-retarding-device is always preserved, and it is impossible for thejack to drop. Furthermore, by utilizing connections from the screwto the fluid-retardingdevice of a speed-multiplying and power-reducing nature, so that the strain on the device is slight, its effectiveness is increased, and it can therefore be of small size and inexpensive construction, or of a design which otherwise would not be efficient.

In the accompanying, drawings, forming apart hereofz y p, V

Fig. lis a central vertical section'through a jack embodying the invention, parts in the tlIlIlGX chamber being shown as if thesection Fig. 1 is a horizontal section taken on the line 4ll of Fig. 1; and

Fig. 5 is a detailhorizontal section show ing a modification;

The ack has a hollow standard 2 and an annex chamber 3 toward the bottom. The casing thus formed.

screw member,

base 1, provided with a J can be madetight enough to hold a supply of lubricant, which may be the same as the fluid in the holdingand lowering device, or a separate fluid may be used'in the device,

projecting into a vertical groove 8 in the side of the ram.

The ram is hollow and its lower portion holds, or is formed as, a nut 9, or nonrotary screw member. A male screw 10 is supported 'rotatably on the base upon a ball bearing 11, and passes upward through the nut into the interior of the ram. 7

The screw 10 is rotated to effect lifting through a. horizontal main operating shaft 12 journaled in bearings 13 and 14: in the outer and inner portions of the annex, and having on its inner end a bevel pinion 15 whichfmeshes with a larger bevel gear 16 fixed on the lower portion of the rotary The projecting outer end 17 of the operating. shaft carries a custom ary ratchet lever device not shown), whereby rotary movement of the screw 1n one diiection, the lifting direction, is produced by oscillatory movement of a removable bar.

The threads of the screw, meanlng thereby the two screw members, are to be understood as being of steep pitch, that is to say,

beyond the angle of repose, so that the jack willrun down'by itself under load,if not held. At such time, through the relative vertical movement of the rotary and nonrotary screw members, the screwjlO is rotated by the load in the direction reverse to that of lifting, and this in turn rotates the shaft 12 in the run-down or lowering direction.

An auxiliary shaft 18, for holding and lowering, 1s 1ournaled 1n bearmgs 19, 2.0 in the annex chamber, transversely to the main operating shaft; and lined on this shaft and held against longitudinal movement by the bearings 1s a worm 21, which meshes with a worm-wheel 22 :fixedto the main shaft.

The worm-wheel and worm are also of comparatively steep pitch, so that the worm will be rotated by the worm-wheel.

Connected with the shaft 18 is a continuous-acting fluid-retarding device 25. The form of this device may be varied. As illustrated, it comprises a dash-pot device having a pair of parallel cylinders 26 formed in a block. On the shaft 18 there is an eccentric 23, the eccentric strap and pitman 24 of which is pivotally connected with two pistons 2? working in the cylinders 26. The piston rods 28 are connected by a walking beam or two-armed link 29, which is pivotally supported at the center on a bracket 30, so that the pistons are compelled to move in opposite directions.

The pistons are preferably provided with packings 31 arranged to make a tight sliding fit with the cylinder walls on the downward or pressure strokes; and the cylinders, or their pressure chambers beneath the pistons are filled with a fluid, more particularly a liquid, such as oil. The said chambers, beyond the ends of the pressure strokes of the pistons, are connected by a constantly open restricted passage 33, also filled with the fluid.

From the foregoing it will be perceived that the movement of the loaded ram when descending will be transmitted through the speedanultiplying connections comprising the screw members and the gears 16, 15, 22, 21, to the fluid-retarding device, causing the pistons to work back and forth andforce the small confined body of fluid through the restricted passage, alternately from one chamber to the other, and that in this way the jack will be restrained to a safe and substantially uniform speed of lowering.

A. one-wayact-ing clutch is interposed between the main operating shaft 12 and the fluid-retarding-device 25, so that the lifting mechanism can be operated freely to raise the load. Said clutch is preferably arranged upon the auxiliary shaft 18, for a reason which will hereinafter appear. The eccentric is accordingly shown as being loose in respect to rotation upon the shaft 18 and united with a pawl carrier 41, the springpressed pawls 42 of which coact with a ratchet-wheel 43 fixed to the shaft. The relation of the teeth is such, it will be understood, that the shaft turns freely within, the stationary eccentric in the lifting operation, but is coupled thereto in respect to pressure and rotation in the opposite direction. A spacer sleeve 4 ion the shaft, between the worm 21 and the pawl-carrier and eccentric member, serves, in connection with the inward projection of the bearing 20, to keep I the said member against axial displacement.

The holding and releasing device .is advantageously arranged to act upon the pawlcarrier member 41, for which purpose this member is formed eXteriorly to constitute a brake-drum, with which cooperates a brakcband 48. The end lugs 49 of this band are shown supported on a rod 50 forming an extension of a screw 51, which passes through a threaded opening in the upper part of the annex chamber 3, and is provided. at its outer end with a handle 52. Turning this handle in one direction sets the brake upon the drum, thereby holding the same against rotation by the load, while turning it in the opposite direction releases the band, permitting it to be opened by a spring 53, whereupon the jack if loaded will descend at the rate permitted by the fluid-retardingdevice, until the brake is again applied to stop the load, or the load reaches a support.

One end 16 of the shaft 18 extends outside of the casing and is made polygonal in order that it may receive a crank-handle 17, seen in Fig. 2. The shaft 18 being positively geared to the main operating shaft 12, in respect to rotation in both directions, (the oneway-acting clutch being between shaft 18 and the holding and lowering means), it is thus possible quickly to run the jack up to the load, preparatory to lifting, and also to run it down when unloaded, in which event the weight of the ram is likely to be insu'ilieient to cause it to go down by itself.

I do not limit myself to the particular fluid used in the fluid-retarding-device, or even necessarily to the employment of a liquid, since with the device geared to the screw so that it operates at comparatively high speed and low pressure, the pistons might, with appropriate modification, work on air, either atmospheric or confined, or other gas; and in that event the retardation could be realized partly or largely by compression or rarefication of the gas, or both, instead of merely by the delaying action of fluid obliged to pass through a restricted passage, as in a liquid dash-pot.

Fig. 5 illustrates an adjusting device by means of which the size of the restricted pas sage 38 can be varied, either for different fluids or for different speeds of lowering.

What I claim as new is:

1. In a self-lowering jack, having a base and a vertically movable load member, vertical screw means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, a hold ing device, and a fluid-retarding-device operatively connected with said screw so as to be driven by the rotation thereof in the lowering operation.

2. In a self-lowering jack, having a base and a vertically movable load member, vertical screw means for lifting comprising ascrew which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, a

holdin device andv a continuo-usaction' flnid-retarding-device geared to said screw.

4. In a self-lowering jack, having a base and a vertically movable load member, vertical scr w means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, mechanism comprising multiplylng gearlng and a one-way-acting clutch adapted to be driven by the screw, and a co-ntimious-action dashpot connected with said mechanism.

5. In a self-lowering jack, having a base and a vertically movable load member, vertical screw means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, a main operating shaft geared to the screw, an auxiliary shaft geared to the main shaft, a rotary member coaxial with the auxiliary shaft, a one way-acting clutch between said member and the auxiliary shaft, a mechanical brake cooperating with said member,

vice connected with the member.

6. In a self-lowermg 1ack, having a base and a vertically movable load member, vertical screw means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, gearing and a one-way-acting clutch connected with the screw, a holding and releasing device, and a dash-pot device connected with said gearing, said dash-pot device comprising a pair of cylinders with an open restricted connecting passage and a pair of pistons connected to move oppositely.

7. In a self-lowering jack, having a base and a vertically movable load member, vertical screw means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, a holding device, a continuous-action fluid-retarding-device containing a confined body of fluid, and multiplying gearing and a one way-acting clutch for driving said fluid-retarding-device from the screw.

8.In a self-lowering jack, having a base and a vertically movable load member, vertical screw means for lifting comprising a screw which is rotated in one direction to effect lifting and in the opposite direction by the action of the load in lowering, gearing and a one-way-acting clutch connected with the screw, a holding and releasing device, and a double-acting dash-pot comprising two cylinder chambers with. a connecting passage and reciprocatory piston means operated through. said gearing and clutch.

JOHN G. KoPF; 

